We developed new seat evaluation methods based on the interaction between the human body and the seat. First, for static sitting comfort, we established the seat compliance as a new evaluation index by using the human body pressure distribution that is calculated by dividing the seat into 16 segments and observed the seat deformation. Secondly, for the dynamic riding comfort, the change in the body pressure distribution was selected as a new index. In the long-term sitting fatigue, physiological data such as stress hormone concentration and electromyogram were made available as indices. Finally, in order to quantify the conventional sensory evaluation, we carried out matching between our physical and physiological data and the subjective judgements.